Muffler and noise screen



Sept. 20, 1955 A. KIMBAL MUFFLER AND NOISE SCREEN Filed Sept. 23, 1952 INVENTOR- W /MZ United States Patent 2,718,274 MUFFLER AND N (118E SCREEN Alfred Kimbal, New York, N. Y. Application September 23, 1952, Serial No. 311,080 2 Claims. (Cl. 181-63) My invention relates to improvements in muffiers and noise screens in which a gas carrying sound waves flows through a number of chambers and noise screens provid ing a large cross sectional area with corresponding slowing of the velocity of the flow; and the objects of my improvement are first to diminish the intensity of the sound waves mainly through their dissipation by repeated reflection and/ or absorption; second to lower the pressure peaks of the gas (if the flow is intermittent) by dividing the gas into equal streams and guiding them into head-on collision; and third, to avoid building up back pressure on the gas by restricting the passages only to accomplish some uniformity of distribution over the entire area of the screen.

1 attain these objects by the device illustrated in the accompanying drawing, in which Figure 1 is an end view of the entire device and a section on line 1-1, Fig. 2; Fig. 2 is an elevation and a section on line 22, Fig. 1; Fig. 3 is a section on line 3-3, Fig. 2.

Similar numerals refer to similar parts throughout the several views.

A housing 1 has its ends covered by end plates 2 and 3. An inlet pipe 4 is attached to and passes through end plate 2, and an outlet pipe 5 is similarly attached to end plate 3.

The noise-carrying gases are inleted into an expansion chamber bounded by part of housing 1 and part of end plates 2 and 3 and by noise screen 6. Noise screen 6 presents an unbroken and continuous reflective surface to sound waves impinging upon it at right angles. All such waves are dissipated therefore by repeated reflection. Screen 6 might be made of any material with suitable strength and heat resistant characteristics and if machine steel were used, the circular openings whose axes are parallel to the surface of screen 6 could be described as sheared and formed. The controlling factors in the size and number of these openings are: (1) the total crosssectional area of all the openings must be sufficient to avoid unpleasant whistling through them and (2) each must be kept to a sufficiently small area so that gases passing through are distributed quite equally through all the openings.

The gases passing through the first noise screen 6 are divided into pairs of equal columns. Upon emerging from screen 6, the members of each pair of columns meet in head-on collision. This collision reduces the peak pressures, and spreads the lowered peaks. The colliding columns of gas fanning out against each other, spread in a plane perpendicular to the direction of the emergent columns. The second noise screen 7 is so located with respect to the first noise screen 6 that the gases impinge upon it midway between two pairs of passages of said noise screen 7. This insures the maximal reflection of sound waves from the surface of this screen and their dissipation in the chamber bounded by noise screens 6 and 7 and part of end plates 2 and 3.

Noise screen 7 is identical to noise screen 6. However, when gases with high intermittent peaks are cooling while passing through the mufiler, it would be advantageous to make the passages through noise screen 7 somewhat smaller than through noise screen 6 because of the progressive contraction of these gases as they cool, and also because of the more continuous flow of the gases after their peaks have been treated to the first head-on collision.

U conical or other curved or bent surface.

Patented Sept. 20, 1955 Gases leaving screen 7 fan out in an accumulator chamber bounded by noise screen 7, part of housing 1, and part of end plates 2 and 3. Maximal dissipation of sound waves occurs in this chamber because of the repeated reflection of the sound Waves from its Walls. The

gases pass from this chamber through outlet pipe 5.

It should be noted that any number of noise screens similar to parts 6 and 7 might be placed parallel to each other. The noise screen might be made cylindrical or Two or more noise screens might be arranged concentrically so that the contracting gases would move from the outermost screen through to the central noise screen to which the outlet pipe would be connected. It should be noted that the noise screens 6 and 7 are spot-welded to housing 1 but this has not been shown as the various parts might be attached together by any means the manufacturer finds most convenient.

Noise screens similar to parts 6 and 7 are useful in Windows or in air ducts to stop noises from entering. When used in outside windows, an outer rain screen should be added. A rain screen would have all of its passages opening downward on the outside and upward on the inside so as to prevent falling rain from entering the noise screen.

Mufflers containing noise screens similar to parts 6 and 7 can also be used as gun silencers if a bullet clearance tube or opening is provided through end plate 3 and a sighting tube provided extending through the entire mufiler from the plate 2 through end plate 3.

I claim:

1. The combination of a mufller with a noise screen through which noise carrying gases pass; said noise screen containing equally spaced circular openings whose planes are perpendicular to the plane of the noise screen; said circular openings being bisected by the plane of the screen and forming the ends of semi-cyclindrical surfaces with a common axis and equal radii protruding alternately from both sides of the screen, and extending across the width of the screen; with similarly arranged parallel groups of these semi-cylindrical surfaces equally spaced, protruding from both sides of the noise screen for the length of the screen; the gases emerging from said screen issuing in pairs of opposing streams which meet in head-on collision.

2. The combination of a mufiler with two or more noise screens through each of which the gases pass in succession; each said noise screen containing equally spaced circular openings Whose planes are perpendicular to the plane of the noise screen; said circular openings being bisected by the plane of the screen and forming the ends of semi-cylindrical surfaces with a common axis and equal radii protruding alternately from both sides of the screen, and extending across the width of the screen; with similarly arranged parallel groups of these semi-cylindrical surfaces equally spaced, protruding from both sides of the noise screen for the length of the screen; the gases emerging from said screen issuing in pairs of opposing streams which meet in head-on collision.

References Cited in the file of this patent UNITED STATES PATENTS 871,775 Blanchard et a1 Nov. 26, 1907 1,026,301 Caldwell et a1 May 14, 1912 1,370,197 De Bolotoff Mar. 1, 1921 1,462,158 Wildner July 17, 1923 1,522,111 Philipson Jan. 6, 1925 1,682,316 Williams Aug. 28, 1928 1,704,608 Humphries Mar. 5, 1929 2,457,890 Hendrick Jan. 4, 1949 FOREIGN PATENTS 26,860 Australia June 2, 1930 

